[PATCH 3/3] Zack's core aio changes to support vectored AIO.

From: Badari Pulavarty
Date: Thu Feb 02 2006 - 11:14:00 EST

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In reply to: Badari Pulavarty: "[PATCH 2/3] Remove readv/writev methods and use aio_read/aio_writeinstead."
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This work is initailly done by Zack Brown to add support for
vectored aio. These are the core changes for AIO to support
IOCB_CMD_PREADV/IOCB_CMD_PWRITEV.

Zack, can you please review the changes as I took most of the
core changes and incorporated into my set. And also could we
further colapse aio_pread/aio_write also into aio_rw_vect_retry() ?
BTW, I haven't done any testing on vectored AIO since I don't have
user-level library changes :(
Please do.

Thanks,
Badari

This work is initailly done by Zack Brown to add support for
vectored aio. These are the core changes for AIO to support
IOCB_CMD_PREADV/IOCB_CMD_PWRITEV.

Zack, can you please review the changes as I took most of the
core changes and incorporated into my set. And also could we
further colapse aio_pread/aio_write also into aio_rw_vect_retry() ?
BTW, I haven't done any testing on vectored AIO :( Please do.

Signed-off-by: Badari Pulavarty <pbadari@xxxxxxxxxx>
Index: linux-2.6.16-rc1.quilt/fs/aio.c
===================================================================
--- linux-2.6.16-rc1.quilt.orig/fs/aio.c 2006-02-01 11:04:28.000000000 -0800
+++ linux-2.6.16-rc1.quilt/fs/aio.c 2006-02-01 14:25:32.000000000 -0800
@@ -416,6 +416,7 @@
req->ki_retry = NULL;
req->ki_dtor = NULL;
req->private = NULL;
+ req->ki_iovec = NULL;
INIT_LIST_HEAD(&req->ki_run_list);

/* Check if the completion queue has enough free space to
@@ -461,6 +462,7 @@

if (req->ki_dtor)
req->ki_dtor(req);
+ kfree(req->ki_iovec);
kmem_cache_free(kiocb_cachep, req);
ctx->reqs_active--;

@@ -1302,6 +1304,64 @@
return -EINVAL;
}

+static void aio_advance_iovec(struct kiocb *iocb, ssize_t ret)
+{
+ struct iovec *iov = &iocb->ki_iovec[iocb->ki_cur_seg];
+
+ BUG_ON(ret <= 0);
+
+ while (iocb->ki_cur_seg < iocb->ki_nr_segs && ret > 0) {
+ ssize_t this = min(iov->iov_len, (size_t)ret);
+ iov->iov_base += this;
+ iov->iov_len -= this;
+ iocb->ki_left -= this;
+ ret -= this;
+ if (iov->iov_len == 0) {
+ iocb->ki_cur_seg++;
+ iov++;
+ }
+ }
+
+ /* the caller should not have done more io than what fit in
+ * the remaining iovecs */
+ BUG_ON(ret > 0 && iocb->ki_left == 0);
+}
+
+static ssize_t aio_rw_vect_retry(struct kiocb *iocb)
+{
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ ssize_t (*rw_op)(struct kiocb *, const struct iovec *,
+ unsigned long, loff_t);
+ ssize_t ret = 0;
+
+ if (iocb->ki_opcode == IOCB_CMD_PREADV)
+ rw_op = file->f_op->aio_read;
+ else
+ rw_op = file->f_op->aio_write;
+
+ do {
+ ret = rw_op(iocb, &iocb->ki_iovec[iocb->ki_cur_seg],
+ iocb->ki_nr_segs - iocb->ki_cur_seg,
+ iocb->ki_pos);
+ if (ret > 0)
+ aio_advance_iovec(iocb, ret);
+
+ /* retry all partial writes. retry partial reads as long as its a
+ * regular file. */
+ } while (ret > 0 && iocb->ki_left > 0 &&
+ (iocb->ki_opcode == IOCB_CMD_PWRITEV ||
+ (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode))));
+
+ /* This means we must have transferred all that we could */
+ /* No need to retry anymore */
+ if ((ret == 0) || (iocb->ki_left == 0))
+ ret = iocb->ki_nbytes - iocb->ki_left;
+
+ return ret;
+}
+
/*
* aio_p{read,write} are the default ki_retry methods for
* IO_CMD_P{READ,WRITE}. They maintains kiocb retry state around potentially
@@ -1393,6 +1453,27 @@
return ret;
}

+static ssize_t aio_setup_vectored_rw(struct kiocb *kiocb)
+{
+ ssize_t ret;
+
+ ret = rw_copy_check_uvector((struct iovec __user *)kiocb->ki_buf,
+ kiocb->ki_nbytes, 0, NULL,
+ &kiocb->ki_iovec);
+ if (ret < 0)
+ goto out;
+
+ kiocb->ki_nr_segs = kiocb->ki_nbytes;
+ kiocb->ki_cur_seg = 0;
+ /* ki_nbytes/left now reflect bytes instead of segs */
+ kiocb->ki_nbytes = ret;
+ kiocb->ki_left = ret;
+
+ ret = 0;
+out:
+ return ret;
+}
+
/*
* aio_setup_iocb:
* Performs the initial checks and aio retry method
@@ -1434,6 +1515,28 @@
if (file->f_op->aio_write)
kiocb->ki_retry = aio_pwrite;
break;
+ case IOCB_CMD_PREADV:
+ ret = -EBADF;
+ if (unlikely(!(file->f_mode & FMODE_READ)))
+ break;
+ ret = aio_setup_vectored_rw(kiocb);
+ if (ret)
+ break;
+ ret = EINVAL;
+ if (file->f_op->aio_read)
+ kiocb->ki_retry = aio_rw_vect_retry;
+ break;
+ case IOCB_CMD_PWRITEV:
+ ret = -EBADF;
+ if (unlikely(!(file->f_mode & FMODE_WRITE)))
+ break;
+ ret = aio_setup_vectored_rw(kiocb);
+ if (ret)
+ break;
+ ret = EINVAL;
+ if (file->f_op->aio_write)
+ kiocb->ki_retry = aio_rw_vect_retry;
+ break;
case IOCB_CMD_FDSYNC:
ret = -EINVAL;
if (file->f_op->aio_fsync)
Index: linux-2.6.16-rc1.quilt/include/linux/aio.h
===================================================================
--- linux-2.6.16-rc1.quilt.orig/include/linux/aio.h 2006-01-16 23:44:47.000000000 -0800
+++ linux-2.6.16-rc1.quilt/include/linux/aio.h 2006-02-01 14:58:08.000000000 -0800
@@ -112,6 +112,9 @@
long ki_retried; /* just for testing */
long ki_kicked; /* just for testing */
long ki_queued; /* just for testing */
+ struct iovec *ki_iovec;
+ unsigned long ki_nr_segs;
+ unsigned long ki_cur_seg;

struct list_head ki_list; /* the aio core uses this
* for cancellation */
Index: linux-2.6.16-rc1.quilt/include/linux/aio_abi.h
===================================================================
--- linux-2.6.16-rc1.quilt.orig/include/linux/aio_abi.h 2006-01-16 23:44:47.000000000 -0800
+++ linux-2.6.16-rc1.quilt/include/linux/aio_abi.h 2006-02-01 14:58:42.000000000 -0800
@@ -41,6 +41,8 @@
* IOCB_CMD_POLL = 5,
*/
IOCB_CMD_NOOP = 6,
+ IOCB_CMD_PREADV = 7,
+ IOCB_CMD_PWRITEV = 8,
};

/* read() from /dev/aio returns these structures. */
Index: linux-2.6.16-rc1.quilt/fs/read_write.c
===================================================================
--- linux-2.6.16-rc1.quilt.orig/fs/read_write.c 2006-02-01 11:04:33.000000000 -0800
+++ linux-2.6.16-rc1.quilt/fs/read_write.c 2006-02-01 15:10:42.000000000 -0800
@@ -511,72 +511,103 @@
/* A write operation does a read from user space and vice versa */
#define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)

+ssize_t rw_copy_check_uvector(const struct iovec __user * uvector,
+ unsigned long nr_segs, unsigned long fast_segs,
+ struct iovec *fast_pointer,
+ struct iovec **ret_pointer)
+ {
+ unsigned long seg;
+ ssize_t ret;
+ struct iovec *iov = fast_pointer;
+
+ /*
+ * SuS says "The readv() function *may* fail if the iovcnt argument
+ * was less than or equal to 0, or greater than {IOV_MAX}. Linux has
+ * traditionally returned zero for zero segments, so...
+ */
+ if (nr_segs == 0) {
+ ret = 0;
+ goto out;
+ }
+
+ /*
+ * First get the "struct iovec" from user memory and
+ * verify all the pointers
+ */
+ if ((nr_segs > UIO_MAXIOV) || (nr_segs <= 0)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ if (nr_segs > fast_segs) {
+ iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
+ if (iov == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
+ if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ /*
+ * According to the Single Unix Specification we should return EINVAL
+ * if an element length is < 0 when cast to ssize_t or if the
+ * total length would overflow the ssize_t return value of the
+ * system call.
+ */
+ ret = 0;
+ for (seg = 0; seg < nr_segs; seg++) {
+ void __user *buf = iov[seg].iov_base;
+ ssize_t len = (ssize_t)iov[seg].iov_len;
+
+ /* see if we we're about to use an invalid len or if
+ * it's about to overflow ssize_t */
+ if (len < 0 || (ret + len < ret)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ if (unlikely(!access_ok(vrfy_dir(type), buf, len))) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ ret += len;
+ }
+out:
+ *ret_pointer = iov;
+ return ret;
+}
+
+/* A write operation does a read from user space and vice versa */
+#define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)
+
static ssize_t do_readv_writev(int type, struct file *file,
const struct iovec __user * uvector,
unsigned long nr_segs, loff_t *pos)
{
- size_t tot_len;
+ ssize_t tot_len;
struct iovec iovstack[UIO_FASTIOV];
struct iovec *iov = iovstack;
ssize_t ret;
- int seg;
io_fn_t fn;
iov_fn_t fnv;

- /*
- * SuS says "The readv() function *may* fail if the iovcnt argument
- * was less than or equal to 0, or greater than {IOV_MAX}. Linux has
- * traditionally returned zero for zero segments, so...
- */
- ret = 0;
- if (nr_segs == 0)
- goto out;
-
- /*
- * First get the "struct iovec" from user memory and
- * verify all the pointers
- */
- ret = -EINVAL;
- if ((nr_segs > UIO_MAXIOV) || (nr_segs <= 0))
- goto out;
- if (!file->f_op)
+ if (!file->f_op) {
+ ret = -EINVAL;
goto out;
- if (nr_segs > UIO_FASTIOV) {
- ret = -ENOMEM;
- iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
- if (!iov)
- goto out;
}
- ret = -EFAULT;
- if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector)))
+
+ ret = rw_copy_check_uvector(uvector, nr_segs, ARRAY_SIZE(iovstack),
+ iovstack, &iov);
+
+ if (ret < 0)
goto out;

- /*
- * Single unix specification:
- * We should -EINVAL if an element length is not >= 0 and fitting an
- * ssize_t. The total length is fitting an ssize_t
- *
- * Be careful here because iov_len is a size_t not an ssize_t
- */
- tot_len = 0;
- ret = -EINVAL;
- for (seg = 0; seg < nr_segs; seg++) {
- void __user *buf = iov[seg].iov_base;
- ssize_t len = (ssize_t)iov[seg].iov_len;
-
- if (len < 0) /* size_t not fitting an ssize_t .. */
- goto out;
- if (unlikely(!access_ok(vrfy_dir(type), buf, len)))
- goto Efault;
- tot_len += len;
- if ((ssize_t)tot_len < 0) /* maths overflow on the ssize_t */
- goto out;
- }
- if (tot_len == 0) {
- ret = 0;
+ if (ret == 0)
goto out;
- }

+ tot_len = ret;
ret = rw_verify_area(type, file, pos, tot_len);
if (ret < 0)
goto out;
@@ -608,9 +639,6 @@
fsnotify_modify(file->f_dentry);
}
return ret;
-Efault:
- ret = -EFAULT;
- goto out;
}

ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
Index: linux-2.6.16-rc1.quilt/include/linux/fs.h
===================================================================
--- linux-2.6.16-rc1.quilt.orig/include/linux/fs.h 2006-02-01 11:04:33.000000000 -0800
+++ linux-2.6.16-rc1.quilt/include/linux/fs.h 2006-02-01 15:12:51.000000000 -0800
@@ -1048,6 +1048,11 @@

struct seq_file;

+ssize_t rw_copy_check_uvector(const struct iovec __user * uvector,
+ unsigned long nr_segs, unsigned long fast_segs,
+ struct iovec *fast_pointer,
+ struct iovec **ret_pointer);
+
extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t vfs_readv(struct file *, const struct iovec __user *,

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Previous message: Kirill Korotaev: "[RFC][PATCH 1/7] VPIDs: add VPID config option"
In reply to: Badari Pulavarty: "[PATCH 2/3] Remove readv/writev methods and use aio_read/aio_writeinstead."
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